How come it keeps on increasing?

K so I got the iPhone 5 a few days ago and I signed the contract with 500MB data usage and today I downloaded Roblox(for my little brother) Minecraft (for my little brother) NHL Gamecenter and Hexic Flow, THAT'S IT! And my data usage is 19MB/500MB. After playing for a few minutes, I turn my phone off for 2 hours. When I turn it back on, it's at 79MB/500MB! Why did it increase? I didn't download anything after that!

Did you have those things playing in the background? Sometimes, apps that were recently used will update itself when turned on. Try turning off the cellular from the settings area.

It also means that your notification and email updates itself. You're going to need to make those things set to manual, so it doesn't update itself every 10 minutes. Also some apps are in the notification area where they connect to the internet and upload stuff. You're going need to turn that off as well.